Xianshi Jin

Long-Term Changes in Fish Assemblage Structure in the Yellow River Estuary Ecosystem, China

Abstract The Yellow River estuary ecosystem is an important spawning ground for many species found in the Bohai Sea and Yellow Sea and contributes substantially to the fishery resource structure and biological reproduction in the northern China Sea. Based on long-term ecosystem surveys in the Yellow River estuary during the main spawning period (May) of most fishery species from 1959 to 2011, the responses of the ecosystem, including regime shifts in species composition, biomass, diversity, and other related factors, were analyzed in this study. Since the 1980s, the dominant large-size species of high economic value (e.g., Largehead Hairtail Trichiurus lepturus) have been replaced by short-lived, low-trophic-level, planktivorous pelagic species (e.g., Scaly Hairfin Anchovy Setipinna taty and Japanese Anchovy Engraulis japonicus). Currently, traditional commercially targeted fishes, such as the Largehead Hairtail, Red Seabream Pagrus major, and Pacific Herring Clupea pallasii, are locally extinct. There has been a rapid shift of dominant species from highly valued, high-trophic-level, large-sized demersal species with complicated age structures to low-value, low-trophic-level, small-sized pelagic species with simple age structures; this shift has resulted in major changes to the ecological cycle and restoration of fishery resources. The fish catch declined from 421.66 kg/h in 1959 to 0.25 kg/h in 2008 and then increased to 3.62 kg/h in 2011. Diversity and evenness indices showed a continuously increasing trend during 1959–2011. The Yellow River estuary may be significantly compromised by overfishing, climate change, dam construction, and pollution, resulting in the decline of traditional fishing industries and reduced biodiversity in this ecosystem.

Trophic interactions, ecosystem structure and function in the southern Yellow Sea

The southern Yellow Sea is an important fishing ground, providing abundant fishery resources. However, overfishing and climate change have caused a decline in the resource and damaged the ecosystem. We developed an ecosystem model to analyze the trophic interactions and ecosystem structure and function to guide sustainable development of the ecosystem. A trophic mass-balance model of the southern Yellow Sea during 2000–2001 was constructed using Ecopath with Ecosim software. We defined 22 important functional groups and studied their diet composition. The trophic levels of fish, shrimp, crabs, and cephalopods were between 2.78 and 4.39, and the mean trophic level of the fisheries was 3.24. The trophic flows within the food web occurred primarily in the lower trophic levels. The mean trophic transfer efficiency was 8.1%, of which 7.1% was from primary producers and 9.3% was from detritus within the ecosystem. The transfer efficiency between trophic levels II to III to IV to V to >V was 5.0%, 5.7%, 18.5%, and 19.7%–20.4%, respectively. Of the total flow, phytoplankton contributed 61% and detritus contributed 39%. Fishing is defined as a top predator within the ecosystem, and has a negative impact on most commercial species. Moreover, the ecosystem had a high gross efficiency of the fishery and a high value of primary production required to sustain the fishery. Together, our data suggest there is high fishing pressure in the southern Yellow Sea. Based on analysis of Odum’s ecological parameters, this ecosystem was at an immature stage. Our results provide some insights into the structure and development of this ecosystem.

Compound-specific isotopes of fatty acids as indicators of trophic interactions in the East China Sea ecosystem

The composition and compound-specific isotopes of fatty acids were studied within food webs in the East China Sea. Lipid-normalized stable carbon isotopes of total organic carbon had a good correlation with trophic level. Variations in fatty acid compositions among diff erent species were observed but were unclear. Diff erent dietary structures could be traced from molecular isotopes of selected fatty acids in the Shiba shrimp (Matapenaeus joyneri), the coastal mud shrimp (Solenocera crassicornis) and the northern Maoxia shrimp (Acetes chinensis). Both M. joyneri and S. crassicornis are mainly benthos feeders, while A. chinensis is a pelagic species, although they have a similar fatty acid composition. There was a good correlation for isotopes of arachidonic acid (C20:4n6; ARA) and docosahexaenoic acid (C22:6n3; DHA) among pelagic species from higher trophic levels. The isotopic compositions of DHA in benthic species were more negative than those of pelagic species at the same trophic level. The fact that the diet of benthic species contains more degraded items, the carbon isotopes of which are derived from a large biochemical fraction, may be the reason for this variation. A comparative study of benthic and pelagic species demonstrated the diff erent carbon sources in potential food items and the presence of a more complex system at the water-sediment interface.

A comparative study of spatial interpolation methods for determining fishery resources density in the Yellow Sea

Spatial interpolation is a common tool used in the study of fishery ecology, especially for the construction of ecosystem models. To develop an appropriate interpolation method of determining fishery resources density in the Yellow Sea, we tested four frequently used methods, including inverse distance weighted interpolation (IDW), global polynomial interpolation (GPI), local polynomial interpolation (LPI) and ordinary kriging (OK). A cross-validation diagnostic was used to analyze the efficacy of interpolation, and a visual examination was conducted to evaluate the spatial performance of the different methods. The results showed that the original data were not normally distributed. A log transformation was then used to make the data fit a normal distribution. During four survey periods, an exponential model was shown to be the best semivariogram model in August and October 2014, while data from January and May 2015 exhibited the pure nugget effect. Using a paired-samples t test, no significant differences (P>0.05) between predicted and observed data were found in all four of the interpolation methods during the four survey periods. Results of the cross-validation diagnostic demonstrated that OK performed the best in August 2014, while IDW performed better during the other three survey periods. The GPI and LPI methods had relatively poor interpolation results compared to IDW and OK. With respect to the spatial distribution, OK was balanced and was not as disconnected as IDW nor as overly smooth as GPI and LPI, although OK still produced a few “bull’s-eye” patterns in some areas. However, the degree of autocorrelation sometimes limits the application of OK. Thus, OK is highly recommended if data are spatially autocorrelated. With respect to feasibility and accuracy, we recommend IDW to be used as a routine interpolation method. IDW is more accurate than GPI and LPI and has a combination of desirable properties, such as easy accessibility and rapid processing.

Genetic diversity analysis of spawner and recaptured populations of Chinese shrimp (Fenneropenaeus chinensis) during stock enhancement in the Bohai Bay based on an SSR marker

Eight microsatellite markers were used to analyze genetic diversity, level of inbreeding, and effective population size of spawner and recaptured populations of Chinese shrimp (Fenneropenaeus chinensis) during stock enhancement in the Bohai Bay in 2013. A total of 254 and 238 alleles were identified in the spawner and recaptured populations, respectively, and the numbers of alleles (Na) were 8–63 and 6–60, respectively. The numbers of effective alleles (Ne) were 2.52–21.60 and 2.67–20.72, respectively. The polymorphism information content ranged from 0.529 to 0.952. The observed heterozygosity (Ho) values (0.638–0.910 and 0.712–0.927) were lower than the expected heterozygosity (He) values (0.603–0.954 and 0.625–0.952), which indicated that the two populations possessed a rich genetic diversity. In 16 tests (2 populations×8 loci), 13 tests deviated from the Hardy-Weinberg equilibrium. Fis values were positive at seven loci and the inbreeding coefficients (F) of the two populations estimated by trioML were 13.234% and 11.603%, suggesting that there was a relatively high degree of inbreeding. A certain level of inbreeding depression had occurred in the Chinese shrimp population. Fst values ranged from 0 to 0.059, with a mean of 0.028, displaying a low level of genetic differentiation in the two populations. Effective population sizes (3 060.2 and 3 842.8) were higher than the minimum number suggested for retaining the evolutionary potential to adapt to new environmental conditions. For enhancement activity in 2014, the ideal number of captured shrimp spawners should have ranged from 7 686 to 19 214 to maintain genetic diversity and effective population size. Further strategies to adjust the balance of economic cost, fishing effort and ideal number of shrimp spawners to maintain a satisfactory effective population size for ensuring the sustainability of Chinese shrimp are proposed.

Feeding habits and ontogenetic diet shifts of Bombay duck, Harpadon nehereus

Based on two bottom trawl surveys conducted in autumn 2000 and 2001, a total of 1106 stomach samples of Bombay duck Harpadon nehereus between 23–278 mm fork length were collected and analyzed. The results show that Bombay duck prey items consisted of 11 groups or 32 species, of which Apogon lineatus, Leptochela gracilis, Acetes chinensis, and Euphausia pacifi ca were the dominant prey species. Ontogenetic variations were found in feeding habits and feeding activity of Bombay duck. Feeding activity was highest in fish smaller than 50 mm, lowest in fish between 50 and 99 mm, and then increased with increasing size thereafter. As Bombay duck size increased, fish prey increased in importance, whereas euphausiids and decapods decreased in importance. Different trophic guilds were observed in feeding habits across the examined size range. Bombay duck smaller than 50 mm were zooplanktivores, mainly feeding on zooplankton and fish larva; those between 50 and 149 mm were generalist predators, mainly feeding on pelagic shrimps, demersal shrimps and fishes; and those larger than 150 mm were piscivores, mainly feeding on fishes.

Spatial variation of crustacean community structure in Yellow Sea and Bohai Sea in spring

Based on the data collected from bottom trawl surveys in Yellow Sea and Bohai Sea in May 2010,the community structure of crustaceans in different regions of Yellow Sea and Bohai Sea was analyzed.We collected a total of 32 crustacean species,including 18 species of shrimp,13 species of crab,and 1 species of squill.The dominant species changed among different regions.The Crangon affinis which was the most important crustacean species in ecosystem was dominant species in all regions of Yellow Sea and Bohai Sea.We studied the composition of average relative density of crustaceans,and found that the biomass of crab was highest in all regions,the average relative biomass of crab was 2.97 kg/h,the individual number of shrimp was the highest in all regions,and the average value was 1 825 ind/h.We also studied the spatial distribution of crustaceans,and found that the sequence by biomass was Northern Yellow Sea southern Yellow Sea middle Yellow Sea Bohai Sea.The diversity of crustaceans in Yellow Sea and Bohai Sea was analyzed,and the results suggested that the diversity indexes were the highest in southern Yellow Sea,the lowest in middle Yellow Sea,whether by biomass or by abundance.The community similarity was also analyzed,and the results suggested that the community similarity index was relatively higher among adjacent waters.

Monthly variation in crustacean assemblage (decapod and stomatopod) and its relationships with environmental variables in Laizhou Bay, China

In this study, we investigated the community structure of crustaceans (decapod and stomatopod) inhabiting the sandy mud bottoms of Laizhou Bay (northeastern China) monthly from May 2011 to April 2012. Investigation was stopped from December 2011 to February 2012 because of the extreme weather and sea ice. A total of 205,057 specimens belonging to 31 species (shrimp, 15; crab, 15; and stomatopod, 1) were collected in 148 hauls. From 2011 to 2012, Oratosquilla oratoria was the dominant biomass species (47.80%), followed by Charybdis japonica (15.49%), Alpheus japonicas (12.61%), Portunus trituberculatus (6.46%), and Crangon spp. (4.19%). Crangon spp. was the most dominant species by individual (32.55%). O. oratoria was the most-frequently encountered species (81.76%), followed by Palaemon gravieri (70.95%), C. japonica (65.54%), A. japonicas (62.16%), and P. trituberculatus (54.73%). The biomass density increased from August to September 2011 and decreased from March 2012 to April 2012. The dynamics of the ecological indices evolve in a similar manner, with high values of diversity and evenness and rich species from May to June 2011 and low values from September to October 2011. O. oratoria, C. japonica, and P. trituberculatus differed by biomass data between groups I (samples obtained from September to October 2011) and II (samples in other months). These species contributed more than 70% to the similarity of the crustacean community structure. Furthermore, the subsets of environmental variables that best matched the crustacean-assemblage structure were as follows: water depth (WD) in summer (June to August); sea surface temperature (SST), dissolved oxygen (DO), and WD in autumn (September to November); and DO, salinity, and WD in spring (March to May). The calculated correlation coefficients and significance level were higher in the period of July to August 2011 than in other months. Comparing 2011 to 2012 with 1982 to 1983, the species composition remained stable. However, the dominant species changed significantly. High value and large species, such as F. chinensis, P. trituberculatus, and T. curvirostris, have been replaced by low value and small species (i.e., Crangon spp., P. gravieri, and C. japonica).

Studies on the apoptosis of channel catfish(Ictalurus punetaus) kidney cells induced by channel catfish reovirus

Channel catfish reovirus(CCRV)is the pathogen of the hemorrhage of channel catfish(Ictalurus punctatus Rafinesque),which propagates in the kidney of channel catfish(CCK)cell line.In this study,the evaluation of whether the CCRV could induce the apoptosis of CCK cells was examined by Hoechst33258 staining,DNA fragmentation assay,TUNEL reaction,and flow cytometry analysis using JC-1,etc.The infection test indicated that CCRV caused typical cytopathic effect(CPE)in CCK cells.Chromatin condensation,nuclei marginalization and the apoptotic bodies were observed in Hoechst 33258 staining,and the apoptotic rate increased with the time going of CCRV infection.The DNA fragmentation assay demonstrated that fragmentation was first noted at 12 h post-infection and reached the peak at 72 h post-infection.In addition,genomic DNA was broken and lots of 3′-termianl free-hydroxyl group(-OH)were generated in infected CCK in TUNEL assay.The hypo-diploid fraction was shown in the sub-G1 cells analysis and the apoptotic rate was 53.44% at 48 h post-infection.Furthermore,the change of the mitochondrial membrane potential(MMP)was investigated by flow cytometric analysis with JC-1 fluorescent labeling and the result showed that the membrane permeability and MMP of CCK cells changed significantly at 24 h post-infection.These results demonstrated that CCRV induced apoptosis in CCK cells.Besides,CCRV-induced apoptosis did require the viral replication as the apoptosis was blocked in CCK cells by both heat-inactivated and UV-inactivated virus.

Establishment of a TaqMan real-time PCR assay for detecting the Cyprinid herpesvirus II

A 1 446 bp coding region of Cyprinid herpesvirus Ⅱ(CyHV-2)DNA helicase gene was amplified by PCR and cloned into pMD19T vector for the construction of recombinant plasmid.After being identified and confirmed with PCR reaction,10-fold serial dilutions of recombinant plasmid were used as standard templates for TaqMan real time PCR to quantify the virus genomic copy number and generate standard curve.Herein,a TaqMan real-time PCR of detecting CyHV-2 was developed.It had a good linear relationship between the initial templates and Ct values with a detection range from 1×101 copies/μL to 1×107 copies/μL,the correlation coefficient(R2)was 0.999 1,and the slope value of standard curve was-3.412.The detection results showed that the specificity of this assay was high for CyHV-2 without cross-reactions with DNA templates from KHV and GSIV.The diseased crucian carp from Sheyang and Baoying,Jiangsu Province,were detected with the established method and the results showed that the content of CyHV-2 were 6.89×104 copies/μL and 3.02×102 copies/μL,respectively.The real-time PCR assay described here with high sensitivity and accuracy is considered to be a powerful tool for the rapid detection and quantification of CyHV-2 in fish.